Question

if the common difference of an ap is 3 ,then a20 - a15 is ?????????????? tell me with the process plz...

Answer 1

We know that,
an=a+(n-1)d
So,a20=a+(20-1)(3)
a20=a+19(3)
a20=a+57

Similarly, a15=a+14d
a15=a+14(3)
a15=a+42

Now,a20-a15=(a+57)-(a+42)
=a+57-a-42
=57-42
=15

Answer 2

Answer:

The solution is $a_{20} - a_{15}$ = 15.

Step-by-step explanation:

Concept: We know that in A.P. $a_{n}$ = a + (n-1) d, where,

a is the first term, n is the position of the term in the A.P. and d is the common difference and $a_{n}$ is the nth term.

To find:  $a_{20} - a_{15}$

Solution:

Given, common difference  d = 3,

$a_{20} - a_{15}$

= (a + (20 - 1)d) - (a + (15 - 1)d)

= a + 19 d - a - 14d

= 19d - 14d = 5d = 5 X 3 = 15

Answer = 15.

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